Power amplification circuit

ABSTRACT

Provided is a power amplification circuit that includes: a first transistor that has an emitter to which a first radio frequency signal is supplied, a base to which a first DC control current or DC control voltage is supplied and a collector that outputs a first output signal that corresponds to the first radio frequency signal; a first amplifier that amplifies the first output signal and outputs a first amplified signal; and a first control circuit that supplies the first DC control current or DC control voltage to the base of the first transistor in order to control output of the first output signal.

This application claims priority from Japanese Patent Application No.2016-064501 filed on Mar. 28, 2016. The contents of this application areincorporated herein by reference in its entirety.

BACKGROUND

The present disclosure relates to a power amplification circuit.

A power amplification circuit is used in a mobile communication devicesuch as a cellular phone in order to amplify the power of a radiofrequency (RF) signal to be transmitted to a base station. When aplurality of amplifiers is used together in a power amplificationcircuit for example, a switch is employed to control switching on andoff of the amplifiers in order to reduce current consumption. Forexample, Japanese Unexamined Patent Application Publication No.2000-278109 discloses a high-frequency switch that is formed of twocascode-connected bipolar transistors.

In the high-frequency switch disclosed in Japanese Unexamined PatentApplication Publication No. 2000-278109, an input signal is supplied tothe base of a first-stage bipolar transistor and an output signal isoutput from the collector of a second-stage bipolar transistor inaccordance with a control signal supplied to the base of thesecond-stage bipolar transistor. However, since the two bipolartransistors of the switch are cascode connected with each other, theamplitude of the output signal is restricted by the saturation voltagesof these transistors. Therefore, the amplitude of the output signal isrestricted and the output signal is likely to be distorted when a largesignal is input. Consequently, it is difficult to achieve desiredlinearity characteristics and the operational range in which the switchcan be used is narrow. Furthermore, since the bipolar transistor of thesecond stage needs to be of such a size as to be able to supply acurrent of the same size as the current supplied to the bipolartransistor of the first stage, an increase in circuit area is incurreddue to an increase in the number of elements.

BRIEF SUMMARY

The present disclosure was made in light of the above-describedcircumstances and to provide a power amplification circuit that includesa switch circuit that can be used even when a large signal is input andthat suppresses an increase in circuit area.

A power amplification circuit according an embodiment of the presentdisclosure includes: a first transistor that has an emitter to which afirst radio frequency signal is supplied, a base to which a first DCcontrol current or DC control voltage is supplied and a collector thatoutputs a first output signal that corresponds to the first radiofrequency signal; a first amplifier that amplifies the first outputsignal and outputs a first amplified signal; and a first control circuitthat supplies the first DC control current or DC control voltage to thebase of the first transistor in order to control output of the firstoutput signal.

According to the embodiment of the present disclosure, a poweramplification circuit can be provided that includes a switch that can beused even when a large signal is input and that suppresses an increasein circuit area.

Other features, elements, characteristics and advantages of the presentdisclosure will become more apparent from the following detaileddescription of preferred embodiments of the present disclosure withreference to the attached drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates an example configuration of a power amplificationcircuit according to an embodiment of the present disclosure;

FIG. 2 illustrates an example of the configuration of a control circuit;

FIG. 3 illustrates an example of the configuration of an amplifier;

FIG. 4 illustrates another example configuration of the poweramplification circuit according to an embodiment of the presentdisclosure;

FIG. 5 illustrates another example configuration of the poweramplification circuit according to an embodiment of the presentdisclosure;

FIG. 6 illustrates another example configuration of the poweramplification circuit according to an embodiment of the presentdisclosure;

FIG. 7A is a graph illustrating simulation results of the frequencydependency of insertion loss in a power amplification circuit;

FIG. 7B is a graph illustrating simulation results of the frequencydependency of insertion loss in the power amplification circuit;

FIG. 8A is a graph illustrating simulation results of the frequencydependency of insertion loss in the power amplification circuit;

FIG. 8B is a graph illustrating simulation results of the frequencydependency of insertion loss in the power amplification circuit;

FIG. 9A is a graph illustrating simulation results of the frequencydependency of insertion loss in the power amplification circuit;

FIG. 9B is a graph illustrating simulation results of the frequencydependency of insertion loss in the power amplification circuit;

FIG. 10A is a graph illustrating simulation results of the frequencydependency of insertion loss in the power amplification circuit; and

FIG. 10B is a graph illustrating simulation results of the frequencydependency of insertion loss in the power amplification circuit.

DETAILED DESCRIPTION

Hereafter, an embodiment of the present disclosure will be described indetail while referring to the drawings. Elements that are the same aseach other will be denoted by the same symbols and repeated descriptionthereof will be omitted.

FIG. 1 illustrates an example configuration (power amplification circuit100A) of a power amplification circuit 100 according to an embodiment ofthe present disclosure. The power amplification circuit 100A amplifiesan input signal RF_(in) and outputs an amplified signal RF_(AMP).

As illustrated in FIG. 1, the power amplification circuit 100A includesa bipolar transistor Tr1, a resistance element R1, a capacitor C1, acontrol circuit 110, amplifiers 120 and 121 and matching networks 130,131, 132 and 133.

The input signal RF_(in) (first radio frequency signal) is supplied tothe emitter of the bipolar transistor Tr1 (first transistor) via thematching network 130, a control voltage V_(cont) is supplied to the baseof the bipolar transistor Tr1, and the bipolar transistor Tr1 outputs anoutput signal RF_(out) (first output signal) from the collector thereof.In addition, the emitter of the bipolar transistor Tr1 is DC groundedvia the resistance element R1 and the base of the bipolar transistor Tr1is AC grounded via the capacitor C1. Operation of the bipolar transistorTr1 will be described in detail later.

One end of the resistance element R1 is connected to the emitter of thebipolar transistor Tr1 and the other end of the resistance element R1 isgrounded. The resistance element R1 DC grounds the emitter of thebipolar transistor Tr1.

One end of the capacitor C1 is connected to the base of the bipolartransistor Tr1 and the other end of the capacitor C1 is grounded. Thecapacitor C1 AC grounds the base of the bipolar transistor Tr1.

The control circuit 110 (first control circuit) supplies the controlvoltage V_(cont) (first DC control voltage), which corresponds to avoltage V1 supplied from outside the power amplification circuit 100A,to the base of the bipolar transistor Tr1.

FIG. 2 illustrates an example of the configuration of the controlcircuit 110. As illustrated in FIG. 2, the control circuit 110 includesbipolar transistors 200, 201 and 202 and a resistance element 210.

The bipolar transistors 200 and 201 are each configured to generate avoltage of a prescribed level. Specifically, the collector and the baseof the bipolar transistor 200 are connected to each other (hereafter,“diode connected”), the voltage V1 is supplied to the collector of thebipolar transistor 200 and the emitter of the bipolar transistor 200 isconnected to the collector of the bipolar transistor 201. The bipolartransistor 201 is diode connected, the collector thereof is connected tothe emitter of the bipolar transistor 200 and emitter of the bipolartransistor 201 is connected to ground. Thus, a voltage of a prescribedlevel (for example, around 2.6 V) is generated at the base of thebipolar transistor 200. Diodes may be used instead of the bipolartransistors 200 and 201.

A power supply voltage Vcc is supplied to the collector of the bipolartransistor 202, the base of the bipolar transistor 202 is connected tothe base of the bipolar transistor 200 and the emitter of the bipolartransistor 202 is connected to one end of the resistance element 210.The bipolar transistor 202 supplies the control voltage V_(cont) fromthe emitter thereof to the base of the bipolar transistor Tr1 via theresistance element 210.

Thus, the control circuit 110 forms an emitter-follower-type biascircuit that supplies the control voltage V_(cont) (bias voltage) to thebase of the bipolar transistor Tr1. The control circuit 110 can switchthe bipolar transistor Tr1 on and off by controlling the control voltageV_(cont) supplied to the base of the bipolar transistor Tr1. Thus, thebipolar transistor Tr1 functions as a switch. The control circuit 110can be given a temperature compensation function by forming the controlcircuit 110 using bipolar transistors that are the same as the bipolartransistor Tr1.

Returning to FIG. 1, the amplifiers 120 and 121 form a two-stageamplification circuit. The amplifier 120 (first amplifier) (drive stage)amplifies the output signal RF_(out) (first output signal) input via thematching network 131 and outputs an amplified signal RF_(amp) (firstamplified signal). The amplified signal RF_(amp) output from theamplifier 120 is input to the amplifier 121 via the matching network132. The amplifier 121 (power stage) amplifies the amplified signalRF_(amp) and outputs the amplified signal RF_(AMP) via the matchingnetwork 133. In this embodiment, an example is illustrated in which thenumber of amplifier stages is two, but the number of amplifier stages isnot limited to two and may be one or three or more.

FIG. 3 illustrates an example of the configuration of the amplifier 120.As illustrated in FIG. 3, the amplifier 120 includes a bipolartransistor 300.

The power supply voltage Vcc is supplied to the collector of the bipolartransistor 300 via an inductor 310, the output signal RF_(out) is inputto the base of the bipolar transistor 300 and the bipolar transistor 300has a common emitter. In addition, a bias current Ibias is supplied tothe base of the bipolar transistor 300. The amplified signal RF_(amp) isoutput from the collector of the bipolar transistor 300. In thisembodiment, description is given using a heterojunction bipolartransistor (HBT) as an example of a transistor, but ametal-oxide-semiconductor field effect transistor (MOSFET) may be usedas the transistor instead. In addition, since the configuration of theamplifier 121 is the same as that of the amplifier 120, detaileddescription thereof is omitted.

Returning to FIG. 1, the matching networks (MNs) 130, 131, 132 and 133are provided in order to match impedances between the circuits. Thematching networks 130, 131, 132 and 133 are formed using inductors andcapacitors, for example. The matching network 130 is formed of a highpass filter circuit or a low pass filter circuit, for example.

Operation of the bipolar transistor Tr1 of the power amplificationcircuit 100A is controlled in accordance with the control voltageV_(cont) supplied to the base of the bipolar transistor Tr1.Specifically, when a comparatively high control voltage V_(cont) issupplied to the base of the bipolar transistor Tr1 and the base-emittervoltage of the bipolar transistor Tr1 is higher than a thresholdvoltage, the bipolar transistor Tr1 switches on and the output signalRF_(out) is output. On the other hand, when a comparatively low controlvoltage V_(cont) (for example, 0 V) is supplied to the base of thebipolar transistor Tr1 and the base-emitter voltage of the bipolartransistor Tr1 is lower than the threshold voltage, the bipolartransistor Tr1 switches off and the output signal RF_(out) is notoutput. Thus, the bipolar transistor Tr1 functions as a switch thatcontrols whether the input signal RF_(in) is allowed to passtherethrough in accordance with the control voltage V_(cont).

In this embodiment, the control circuit 110 generates a control voltage,but the control circuit 110 may control operation of the bipolartransistor Tr1 by using a control current (first DC control current)instead of a control voltage. Specifically, the control circuit 110 mayswitch the bipolar transistor Tr1 on by supplying a comparatively largecontrol current (for example, around several hundred μA to 1 mA) to thebase of the bipolar transistor Tr1 and may switch the bipolar transistorTr1 off by supplying a comparatively small control current (for example,around 0 mA) to the base of the bipolar transistor Tr1.

With the above-described configuration, the single bipolar transistorTr1 controls switching on and off of passage of the input signal RF_(in)in the power amplification circuit 100A. Therefore, since there is noneed to cascode connect two bipolar transistors as described in JapaneseUnexamined Patent Application Publication No. 2000-278109, degradationin the form of distortion characteristics caused by a saturation voltagewhen a large signal is input is suppressed compared with theconfiguration described in Japanese Unexamined Patent ApplicationPublication No. 2000-278109. Furthermore, an increase in circuit area issuppressed compared with a configuration in which a switch circuit isprovided outside the power amplification circuit and compared with theconfiguration described in Japanese Unexamined Patent ApplicationPublication No. 2000-278109. Therefore, with the power amplificationcircuit 100A, a power amplification circuit can be provided thatincludes a switch that can be used even when a large signal is input andthat suppresses an increase in circuit area.

FIG. 4 illustrates another example configuration (power amplificationcircuit 100B) of the power amplification circuit 100. Constituentelements that are the same as those of the power amplification circuit100A illustrated in FIG. 1 are denoted by the same symbols anddescription thereof is omitted. In addition, in the embodiment describedhereafter illustration of amplifiers subsequent to the amplifier of thesecond stage is omitted.

A power amplification circuit 100B is formed by connecting n (n is anatural number) power amplification circuits 100A in parallel with eachother for a single input signal RF_(in). Specifically, the poweramplification circuit 100B includes n bipolar transistors Tr1, Tr2, . .. , and Trn, the resistance element R1, n capacitors Ca1, Ca2, . . . ,and Can, n control circuits 110 a 1, 110 a 2, . . . , and 110 an, namplifiers 120 a 1, 120 a 2, . . . , and 120 an, the matching network130 and n matching networks 131 a 1, 131 a 2, . . . , and 131 an.

The input signal RF_(in) is supplied to the commonly connected emittersof the bipolar transistor Tr1 (first transistor), the bipolar transistorTr2 (second transistor), . . . , and the bipolar transistor Trn (nthtransistor) via the matching network 130. In addition, control voltagesV_(cont) 1, V_(cont) 2, . . . , and V_(cont)n generated by the controlcircuits 110 a 1, 110 a 2, . . . , and 110 an are supplied to the basesof the bipolar transistors Tr1, Tr2, . . . , and Trn. The bipolartransistors Tr1, Tr2, . . . , and Trn respectively output output signalsRF_(out) 1 (first output signal), RF_(out) 2 (second output signal), . .. , and RF_(out)n (nth output signal) that correspond to the inputsignal RF_(in) from the collectors thereof.

The configurations of the resistance element R1, the capacitors Ca1,Ca2, . . . , to Can and the matching networks 130, 131 a, 131 a 2, . . ., to 131 an are the same as those in the power amplification circuit100A and therefore detailed description thereof is omitted. In thisembodiment, a plurality of bipolar transistors share a single resistanceelement R1, but a resistance element may instead be provided for eachbipolar transistor.

The control circuit 110 a 1 (first control circuit), the control circuit110 a 2 (second control circuit), . . . , and the control circuit 110 an(nth control circuit) respectively generate voltages that correspond tovoltages Va 1, Va 2, . . . , and Van supplied from outside the poweramplification circuit 100B and supply control voltages V_(cont) 1 (firstDC control voltage), V_(cont) 2 (second DC control voltage), . . . , andV_(cont)n (nth DC control voltage) to the bases of the bipolartransistors Tr1, Tr2, . . . , and Trn. For example, the bipolartransistor Tr1 is turned on by the supply of a comparatively highcontrol voltage V_(cont) 1 and the bipolar transistors Tr2, . . . , andTrn are switched off by the supply of comparatively low control voltagesV_(cont) 2, . . . , and V_(cont)n. Thus, the input signal RF_(in) onlypasses through the bipolar transistor Tr1 and the output signal RF_(out)1 output by the bipolar transistor Tr1 can be selectively supplied tothe amplifier 120 a 1. The configurations of the control circuits 110 a1, 110 a 2, . . . , and 110 an are the same as that of the controlcircuit 110 and therefore detailed description thereof is omitted.

The amplifiers 120 a 1 (first amplifier), 120 a 2 (second amplifier), .. . , and 120 an (nth amplifier) respectively amplify the output signalsRF_(out) 1, RF_(out) 2, . . . , and RF_(out)n input via the matchingnetworks 131 a 1, 131 a 2, . . . , and 131 an and output amplifiedsignals RF_(amp) 1 (first amplified signal), RF_(amp) 2 (secondamplified signal), . . . , and RF_(amp)n (nth amplified signal). Theconfigurations of the amplifiers 120 a 1, 120 a 2, . . . , and 120 anare the same as that of the amplifier 120 and therefore detaileddescription thereof is omitted.

In this configuration as well, each of the bipolar transistors Tr1, Tr2,. . . , and Trn controls switching on and off of passage of the inputsignal RF_(in), similarly to as in the power amplification circuit 100A.Therefore, with the power amplification circuit 100B, a poweramplification circuit can be provided that includes a switch that can beused even when a large signal is input and that suppresses an increasein circuit area. Thus, when an amplification mode (low power mode orhigh power mode, etc.) is to be switched in accordance with the signallevel of the input signal RF_(in), for example, the input signal RF_(in)can be selectively supplied to any of the amplifiers among theamplifiers 120 a 1, 120 a 2, . . . , and 120 an by using the bipolartransistors Tr1, Tr2, . . . , Trn as switches.

FIG. 5 illustrates another example configuration (power amplificationcircuit 100C) of the power amplification circuit 100. Constituentelements that are the same as those of the power amplification circuit100A illustrated in FIG. 1 are denoted by the same symbols anddescription thereof is omitted.

A power amplification circuit 100C is provided with N (N is a naturalnumber) parallel-connected paths (signal input paths) that each containthe components of the power amplification circuit 100A illustrated inFIG. 1 up to the matching network 131 and has a common path after thematching network 131. Specifically, the power amplification circuit 100Cincludes N bipolar transistors TR1, TR2, . . . , and TRN, N resistanceelements R1, R2, . . . , and RN, N capacitors C1, C2, . . . , and CN, Ncontrol circuits 110A1, 110A2, . . . , and 110AN, the amplifier 120, Nmatching networks 130A1, 130A2, . . . , and 130AN and the matchingnetwork 131.

Input signals RF_(IN) 1 (first radio frequency signal), RF_(IN) 2(second radio frequency signal), . . . , and RF_(IN)N (Nth radiofrequency signal) are respectively supplied to the emitters of thebipolar transistors TR1 (first transistor), TR2 (third transistor), . .. , and TRN (Nth transistor) via the matching networks 130A1, 130A2, . .. , and 130AN. In addition, control voltages V_(CONT) 1, V_(CONT) ², . .. , and V_(CONT)N generated by the control circuits 110A1, 110A2, . . ., and 110AN are respectively supplied to the bases of the bipolartransistors TR1, TR2, . . . , and TRN. The bipolar transistors TR1, TR2,. . . , and TRN respectively output output signals RF_(OUT) 1 (firstoutput signal), RF_(OUT) 2 (third output signal), . . . , and RF_(OUT)N(Nth output signal) that correspond to the input signals RF_(IN) 1,RF_(IN) 2, . . . , and RF_(IN)N from the collectors thereof.

The configurations of the resistance elements R1, R2, . . . , and RN,the capacitors C1, C2, . . . , and CN, and the matching networks 130A1,130A2, . . . , 130AN, and 131 are the same as those in the poweramplification circuit 100A and therefore detailed description thereof isomitted.

The control circuits 110A1 (first control circuit), 110A2 (third controlcircuit), . . . , and 110AN (Nth control circuit) respectively generatevoltages that correspond to voltages VA1, VA2, . . . , and VAN suppliedfrom outside the power amplification circuit 100C and supply controlvoltages V_(CONT) 1 (first DC control voltage), V_(CONT) 2 (third DCcontrol voltage), . . . , and V_(CONT)N (Nth DC control voltage) to thebases of the bipolar transistors TR1, TR2, . . . , and TRN. Theconfigurations of the control circuits 110A1, 110A2, . . . , and 110ANare the same as that of the control circuit 110 and therefore detaileddescription thereof is omitted.

The output signals RF_(OUT) 1, RF_(OUT) 2, . . . , and RF_(OUT)N areinput to the amplifier 120 via the matching network 131. The amplifier120 amplifies the output signals and outputs the resulting amplifiedsignal RF_(amp).

In this configuration as well, the bipolar transistors TR1, TR2, . . . ,and TRN control switching on and off of passage of the input signalsRF_(IN) 1, RF_(IN) 2, . . . , and RF_(IN)N, similarly to as in the poweramplification circuit 100A. Therefore, with the power amplificationcircuit 100C, a power amplification circuit can be provided thatincludes a switch that can be used even when a large signal is input andthat suppresses an increase in circuit area. For example, the poweramplification circuit 100C can be applied to a multiband poweramplification circuit in which input signals RF_(IN) 1, RF_(IN) 2, . . ., and RF_(IN)N of different frequencies share a single amplifier 120.

FIG. 6 illustrates another example configuration (power amplificationcircuit 100D) of the power amplification circuit 100. Constituentelements that are the same as those of the power amplification circuit100A illustrated in FIG. 1 are denoted by the same symbols anddescription thereof is omitted.

A power amplification circuit 100D has a configuration obtained bycombining the power amplification circuit 100B illustrated in FIG. 4 andthe power amplification circuit 100C illustrated in FIG. 5.Specifically, the power amplification circuit 100D includes bipolartransistors Tra1, Tra2, Trb1 and Trb2, resistance elements Ra and Rb,capacitors Ca1, Ca2, Cb1 and Cb2, control circuits 110 a 1, 110 a 2, 110b 1 and 110 b 2, amplifiers 120 a and 120 b and matching networks 130 a,130 b, 131 a and 131 b.

An input signal RF_(in)A (first radio frequency signal) is supplied tothe commonly connected emitters of the bipolar transistors Tra1 (firsttransistor) and Tra2 (second transistor) via the matching network 130 a.In addition, control voltages V_(cont)a1 and V_(cont)a2 generated by thecontrol circuits 110 a 1 and 110 a 2 are respectively supplied to thebases of the bipolar transistors Tra1 and Tra2. The bipolar transistorsTra1 and Tra2 respectively output output signals RF_(OUT)A1 (firstoutput signal) and RF_(OUT)A2 (second output signal) corresponding tothe input signal RF_(in)A from the collectors thereof.

Similarly, an input signal RF_(in)B (third radio frequency signal) issupplied to the commonly connected emitters of the bipolar transistorsTrb1 (fourth transistor) and Trb2 (fifth transistor) via the matchingnetwork 130 b. In addition, control voltages V_(cont)b1 and V_(cont)b2generated by the control circuits 110 b 1 and 110 b 2 are respectivelysupplied to the bases of the bipolar transistors Trb and Trb2. Thebipolar transistors Trb and Trb2 respectively output output signalsRF_(OUT)B1 (fourth output signal) and RF_(OUT)B2 (fifth output signal)corresponding to the input signal RF_(in)B from the collectors thereof.

The configurations of the resistance elements Ra and Rb, the capacitorsCa1, Ca2, Cb1 and Cb2 and matching network 130 a, 130 b, 131 a and 131 bare the same as those in the power amplification circuit 100A andtherefore detailed description thereof is omitted.

The control circuits 110 a 1 (first control circuit), 110 a 2 (secondcontrol circuit), 110 b 1 (fourth control circuit) and 110 b 2 (fifthcontrol circuit) respectively supply the control voltages V_(cont)a1(first DC control voltage), V_(cont)a2 (second DC control voltage),V_(cont)b1 (fourth DC control voltage) and V_(cont)b2 (fifth DC controlvoltage) corresponding to the voltages Va1, Va2, Vb1 and Vb2 suppliedfrom outside the power amplification circuit 100D to the bases of thebipolar transistors Tra1, Tra2, Trb1 and Trb2. The configurations of thecontrol circuits 110 a 1, 110 a 2, 110 b 1 and 110 b 2 are the same asthat of the control circuit 110 and therefore detailed descriptionthereof is omitted.

The output signal RF_(out)A1 or the output signal RF_(out)B1 is input tothe amplifier 120 a (first amplifier) via the matching network 131 a.Then, the amplifier 120 a amplifies the output signal and outputs aresulting amplified signal RF_(amp)A (first amplified signal).

Similarly, the output signal RF_(out)A2 or the output signal RF_(out)B2is input to the amplifier 120 b (second amplifier) via the matchingnetwork 131 b. Then, the amplifier 120 b amplifies the output signal andoutputs a resulting amplified signal RF_(amp)B (second amplifiedsignal).

In this configuration as well, switching on and off of passage of theinput signals RF_(in)A and RF_(in)B is controlled by switching on one ofthe bipolar transistors Tra1, Tra2, Trb1 and Trb2, similarly to as inthe power amplification circuit 100A. Therefore, with the poweramplification circuit 100D, a power amplification circuit can beprovided that includes a switch that can be used even when a largesignal is input and that suppresses an increase in circuit area. Inaddition, the input signals RF_(in)A and RF_(in)B can be supplied to theamplifier 120 a or the amplifier 120 b. For example, the poweramplification circuit 100D can be applied to a multimode multiband poweramplification circuit that includes amplifiers 120 a and 120 b for inputsignals RF_(in)A and RF_(in)B of different frequencies, the amplifiers120 a and 120 b operating in different modes, and in which the inputsignals RF_(in)A and RF_(in)B of different frequencies share theamplifiers 120 a and 120 b.

In this embodiment, a configuration in which there are two input pathsand two bipolar transistors are provided for each of the input paths isdescribed as an example, but the number of input paths and the number ofbipolar transistors provided for each input path are not limited to twoand may be one or three or more.

Next, simulation results for the frequency dependency of insertion lossin the power amplification circuit 100D will be described whilereferring to FIGS. 7A to 10B.

FIGS. 7A to 10B are graphs illustrating simulation results of thefrequency dependencies of the insertion losses of the bipolartransistors Tra1, Tra2, Trb1 and Trb2 in the power amplification circuit100D illustrated in FIG. 6. In the graphs illustrated in FIGS. 7A to10B, the vertical axis represents insertion loss (scattering (S)parameter=20 log|S₂₁|) (dB) and the horizontal axis represents thefrequency (GHz) of an input signal. In addition, P1 represents an inputterminal Port 1 of the input signal RF_(in)A, P2 represents an inputterminal Port2 of the input signal RF_(in)B, P3 represents an outputterminal Port 3 of the bipolar transistors Tra1 and Trb1 (amplifier 120a side) and P4 represents an output terminal Port4 of the bipolartransistors Tra2 and Trb2 (amplifier 120 b side) (refer to FIG. 6). TheS parameter of an output terminal with respect to an input terminal isexpressed as dB (S(output terminal, input terminal)).

FIG. 7A illustrates simulation results for dB(S(P3, P1)), dB(S(P3, P2))and dB(S(P3, P4)) for a case where the power amplification circuit 100Dis made to operate such that only the bipolar transistor Tra1 isswitched on and the bipolar transistors Tra2, Trb1 and Trb2 are switchedoff and consequently the input signal RF_(in)A is supplied to theamplifier 120 a. Similarly, FIG. 7B illustrates simulation results fordB(S(P4,P1)), dB(S(P4,P2)) and dB(S(P4,P3)) for the same case. Asillustrated in FIG. 7A, the S parameter dB(S(P3, P1)) of the output ofP3 with respect to the input of P1 is around −2 dB to −5 dB in all thefrequency bands (2.0 to 3.0 GHz). In contrast, the S parameters for P3from P2, P3 from P4, P4 from P1, P4 from P2 and P4 from P3 are smallerthan around −20 dB. Therefore, it is clear that it is possible toselectively supply just the input signal RF_(in)A to the amplifier 120a.

FIG. 8A illustrates simulation results for dB(S(P4, P1)), dB(S(P4, P2))and dB(S(P4, P3)) for a case where the power amplification circuit 100Dis made to operate such that only the bipolar transistor Tra2 isswitched on and the bipolar transistors Tra1, Trb1 and Trb2 are switchedoff and consequently the input signal RF_(in)A is supplied to theamplifier 120 b. Similarly, FIG. 8B illustrates simulation results fordB(S(P3,P1)), dB(S(P3,P2)) and dB(S(P3,P4)) for the same case. Asillustrated in FIG. 8A, the S parameter dB(S(P4, P1)) of the output ofP4 with respect to the input of P1 is around −2 dB to −6 dB in all thefrequency bands. In contrast, the S parameters for P4 from P2, P4 fromP3, P3 from P1, P3 from P2 and P3 from P4 are smaller than around −20dB. Therefore, it is clear that it is possible to selectively supplyjust the input signal RF_(in)A to the amplifier 120 b.

FIG. 9A illustrates simulation results for dB(S(P3, P1)), dB(S(P3, P2))and dB(S(P3, P4)) for a case where the power amplification circuit 100Dis made to operate such that only the bipolar transistor Trb1 isswitched on and the bipolar transistors Tra1, Tra2, and Trb2 areswitched off and consequently the input signal RF_(in)B is supplied tothe amplifier 120 a. Similarly, FIG. 9B illustrates simulation resultsfor dB(S(P4,P1)), dB(S(P4,P2)) and dB(S(P4,P3)) for the same case. Asillustrated in FIG. 9A, the S parameter dB(S(P3, P2)) of the output ofP3 with respect to the input of P2 is around −2 dB to −5 dB in all thefrequency bands. In contrast, the S parameters for P3 from P1, P3 fromP4, P4 from P1, P4 from P2 and P4 from P3 are smaller than around −20dB. Therefore, it is clear that it is possible to selectively supplyjust the input signal RF_(in)B to the amplifier 120 a.

FIG. 10A illustrates simulation results for dB(S(P4, P1)), dB(S(P4, P2))and dB(S(P4, P3)) for a case where the power amplification circuit 100Dis made to operate such that only the bipolar transistor Trb2 isswitched on and the bipolar transistors Tra1, Tra2, and Trb1 areswitched off and consequently the input signal RF_(in)B is supplied tothe amplifier 120 b. Similarly, FIG. 10B illustrates simulation resultsfor dB(S(P3,P1)), dB(S(P3,P2)) and dB(S(P3,P4)) for the same case. Asillustrated in FIG. 10A, the S parameter dB(S(P4, P2)) of the output ofP4 with respect to the input of P2 is around −3 dB to −6 dB in all thefrequency bands. In contrast, the S parameters for P4 from P1, P4 fromP3, P3 from P1, P3 from P2 and P3 from P4 are smaller than around −20dB. Therefore, it is clear that it is possible to selectively supplyjust the input signal RF_(in)B to the amplifier 120 b.

It is clear from the above-described simulation results that it ispossible to selectively supply either of the input signals RF_(in)A andRF_(in)B to either of the amplifiers 120 a and 120 b by turning on oneof the bipolar transistors Tra1, Tra2, Trb1 and Trb2 and turning off therest of the bipolar transistors.

Exemplary embodiments of the present disclosure have been describedabove. The power amplification circuits 100A, 100B, 100C and 100D eachinclude: a bipolar transistor that has an emitter to which a radiofrequency signal is supplied, a base to which a DC control voltage issupplied and a collector from which an output signal corresponding tothe radio frequency signal is output; and a control circuit thatgenerates the DC control voltage. Thus, a single bipolar transistorcontrols switching on and off of passage of an input signal. Therefore,a power amplification circuit can be provided that includes a switchthat can be used even when a large signal is input and that suppressesan increase in circuit area.

Furthermore, in the power amplification circuits 100A, 100B, 100C and100D, the emitter of the bipolar transistor, which functions as aswitch, can be DC grounded via a resistance element and the base of thebipolar transistor can be AC grounded using a capacitor.

The power amplification circuit 100B includes n of each of a bipolartransistor, a control circuit and an amplifier, which are the same asthose of the power amplification circuit 100A, connected in parallelwith each other for a single input signal RF_(in). The emitters of thebipolar transistors are connected to each other and the input signalRF_(in) is supplied to the emitters. Therefore, switching on and off ofthe n bipolar transistors is controlled by the control circuits and theinput signal RF_(in) can be selectively supplied to a prescribedamplifier.

In addition, the power amplification circuit 100C includes a bipolartransistor and a control circuit for each of a plurality of inputsignals RF_(IN) 1, RF_(IN) 2, . . . , and RF_(IN)N. The collectors ofthe bipolar transistors are connected to each other and the bipolartransistors respectively supply the output signals RF_(OUT) 1, RF_(OUT)2, . . . , RF_(OUT)N. Therefore, switching on and off of N bipolartransistors is controlled by the control circuits and it is possible tosupply only a specific input signal to the amplifier 120.

Furthermore, the power amplification circuit 100D includes bipolartransistors Tra1 and Tra2, bipolar transistors Trb1 and Trb2 and controlcircuits 110 a 1, 110 a 2, 110 b 1 and 110 b 2 that control switching onand off of the bipolar transistors for two input signals RF_(in)A andRF_(in)B, the components being similar to those of the poweramplification circuit 100A. Thus, the input signal RF_(in)A or the inputsignal RF_(in) 3 can be supplied to the amplifier 120 a or the amplifier120 b by switching on the appropriate one of the bipolar transistorsTra1, Tra2, Trb1 and Trb2.

Although npn-type bipolar transistors are used in this embodiment,pnp-type bipolar transistors may be used instead of the npn-type bipolartransistors.

The purpose of the embodiments described above is to enable easyunderstanding of the present disclosure and the embodiments are not tobe interpreted as limiting the present disclosure. The presentdisclosure can be modified or improved without departing from the gistof the disclosure and equivalents to the present disclosure are alsoincluded in the present disclosure. In other words, appropriate designchanges made to the embodiments by one skilled in the art are includedin the scope of the present disclosure so long as the changes have thecharacteristics of the present disclosure. For example, the elementsincluded in the embodiments and the arrangements, materials, conditions,shapes, sizes and so forth of the elements are not limited to thoseexemplified in the embodiments and can be appropriately changed. Inaddition, the elements included in the embodiments can be combined asmuch as technically possible and such combined elements are alsoincluded in the scope of the present disclosure so long as the combinedelements have the characteristics of the present disclosure.

While preferred embodiments of the disclosure have been described above,it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the disclosure. The scope of the disclosure, therefore, isto be determined solely by the following claims.

What is claimed is:
 1. A power amplification circuit comprising: a firsttransistor having an emitter to which a first radio frequency signal issupplied, a base to which a first DC control current or DC controlvoltage is supplied, and a collector from which a first output signal isoutput, the first output signal corresponding to the first radiofrequency signal; a first amplifier that amplifies the first outputsignal and outputs a first amplified signal; a first control circuitthat supplies the first DC control current or DC control voltage to thebase of the first transistor thereby controlling supply of the firstoutput signal to the first amplifier; a resistance element; and acapacitor, wherein one end of the resistance element is connected to theemitter of the first transistor and another end of the resistanceelement is grounded, thereby DC grounding the emitter of the firsttransistor, and one end of the capacitor is connected to the base of thefirst transistor and another end of the capacitor is grounded, and as aresult, thereby AC grounding the base of the first transistor.
 2. Thepower amplification circuit according to claim 1, further comprising: asecond transistor having an emitter to which the first radio frequencysignal is supplied and that is DC grounded, a base to which a second DCcontrol current or DC control voltage is supplied and that is ACgrounded, and a collector from which a second output signal is output,the second output signal corresponding to the first radio frequencysignal; a second amplifier that amplifies the second output signal andoutputs a second amplified signal; and a second control circuit thatsupplies the second DC control current or DC control voltage to the baseof the second transistor thereby controlling supply of the second outputsignal to the second amplifier.
 3. The power amplification circuitaccording to claim 2, wherein supply of the first output signal to thefirst amplifier is controlled in accordance with the first DC controlcurrent or DC control voltage, supply of the second output signal to thesecond amplifier is controlled in accordance with the second DC controlcurrent or DC control voltage, and only one of the first output signalis supplied to the first amplifier and the second output signal issupplied to the second amplifier.
 4. The power amplification circuitaccording to claim 1, further comprising: a third transistor having anemitter to which a second radio frequency signal is supplied and that isDC grounded, a base to which a third DC control current or DC controlvoltage is supplied and that is AC grounded, and a collector from whicha third output signal is output, the third output signal correspondingto the second radio frequency signal; and a third control circuit thatsupplies the third DC control current or DC control voltage to the baseof the third transistor, thereby controlling supply of the third outputsignal to the first amplifier.
 5. The power amplification circuitaccording to claim 4, wherein supply of the first output signal to thefirst amplifier is controlled in accordance with the first DC controlcurrent or DC control voltage, supply of the third output signal to thefirst amplifier is controlled in accordance with the third DC controlcurrent or DC control voltage, and only one of the first output signaland the third output signal is supplied to the first amplifier, suchthat the first amplifier amplifies the first or third output signal andoutputs the first amplified signal.
 6. The power amplification circuitaccording to claim 2, further comprising: a fourth transistor having anemitter to which a third radio frequency signal is supplied and that isDC grounded, a base to which a fourth DC control current or DC controlvoltage is supplied and that is AC grounded, and a collector from whicha fourth output signal is output, the fourth output signal correspondingto the third radio frequency signal; a fifth transistor having anemitter to which the third radio frequency signal is supplied and thatis DC grounded, a base to which a fifth DC control current or DC controlvoltage is supplied and that is AC grounded, and a collector from whicha fifth output signal is output, the fifth output signal correspondingto the third radio frequency signal; a fourth control circuit thatsupplies the fourth DC control current or DC control voltage to the baseof the fourth transistor, thereby controlling supply of the fourthoutput signal to the first amplifier; and a fifth control circuit thatsupplies the fifth DC control current or DC control voltage to the baseof the fifth transistor, thereby controlling supply of the fifth outputsignal to the second amplifier.
 7. The power amplification circuitaccording to claim 6, wherein supply of the fourth output signal to thefirst amplifier is controlled in accordance with the fourth DC controlcurrent or DC control voltage, supply of the fifth output signal to thesecond amplifier is controlled in accordance with the fifth DC controlcurrent or DC control voltage, and only one of the first output signaland the fourth output signal is supplied to the first amplifier, andonly one of the second output signal or the fifth output signal issupplied to the second amplifier, such that the first amplifieramplifies the first or fourth output signal and outputs the firstamplified signal, and the second amplifier amplifies the second or fifthoutput signal and outputs the second amplified signal.
 8. The poweramplification circuit according to claim 1, wherein the first controlcircuit comprises a plurality of transistors, the plurality oftransistors being the same type of bipolar transistors as the firsttransistor.
 9. The power amplification circuit according to claim 2,wherein the second control circuit comprises a plurality of transistors,the plurality of transistors being the same type of bipolar transistorsas the second transistor.
 10. The power amplification circuit accordingto claim 4, wherein the third control circuit comprises a plurality oftransistors, the plurality of transistors being the same type of bipolartransistors as the third transistor.
 11. The power amplification circuitaccording to claim 6, wherein the fourth control circuit comprises aplurality of transistors, the plurality of transistors of the fourthcontrol circuit being the same type of bipolar transistors as the firsttransistor, and wherein the fifth control circuit comprises a pluralityof transistors, the plurality of transistors of the fifth controlcircuit being the same type of bipolar transistors as the firsttransistor.
 12. The power amplification circuit according to claim 6,wherein the power amplification circuit is multi-mode, multi-band poweramplifier.
 13. The power amplification circuit according to claim 4,wherein the power amplification circuit is multi-band power amplifier.14. The power amplification circuit according to claim 1, furthercomprising: a second transistor having an emitter to which the firstradio frequency signal is supplied and that is DC grounded, a base towhich a second DC control current or DC control voltage is supplied andthat is AC grounded, and a collector from which a second output signalis output, the second output signal corresponding to the first radiofrequency signal; a second amplifier that amplifies the second outputsignal and outputs a second amplified signal; and a second controlcircuit that supplies the second DC control current or DC controlvoltage to the base of the second transistor thereby controlling supplyof the second output signal to the second amplifier; wherein supply ofthe first output signal to the first amplifier is controlled inaccordance with the first DC control current or DC control voltage,supply of the second output signal to the second amplifier is controlledin accordance with the second DC control current or DC control voltage,and only one of the first output signal is supplied to the firstamplifier and the second output signal is supplied to the secondamplifier.
 15. The power amplification circuit according to claim 1,further comprising: a third transistor having an emitter to which asecond radio frequency signal is supplied and that is DC grounded, abase to which a third DC control current or DC control voltage issupplied and that is AC grounded, and a collector from which a thirdoutput signal is output, the third output signal corresponding to thesecond radio frequency signal; and a third control circuit that suppliesthe third DC control current or DC control voltage to the base of thethird transistor, thereby controlling supply of the third output signalto the first amplifier; wherein supply of the first output signal to thefirst amplifier is controlled in accordance with the first DC controlcurrent or DC control voltage, supply of the third output signal to thefirst amplifier is controlled in accordance with the third DC controlcurrent or DC control voltage, and only one of the first output signaland the third output signal is supplied to the first amplifier, suchthat the first amplifier amplifies the first or third output signal andoutputs the first amplified signal.
 16. The power amplification circuitaccording to claim 14, wherein the first amplifier and the secondamplifier comprise heterojunction bipolar transistors.
 17. The poweramplification circuit according to claim 15, wherein the first amplifierand the second amplifier comprise heterojunction bipolar transistors.18. A power amplification circuit comprising: a first transistor havingan emitter to which a first radio frequency signal is supplied, a baseto which a first DC control current or DC control voltage is supplied,and a collector from which a first output signal is output, the firstoutput signal corresponding to the first radio frequency signal; a firstamplifier that amplifies the first output signal and outputs a firstamplified signal; a first control circuit that supplies the first DCcontrol current or DC control voltage to the base of the firsttransistor thereby controlling supply of the first output signal to thefirst amplifier; a second transistor having an emitter to which thefirst radio frequency signal is supplied and that is DC grounded, a baseto which a second DC control current or DC control voltage is suppliedand that is AC grounded, and a collector from which a second outputsignal is output, the second output signal corresponding to the firstradio frequency signal; a second amplifier that amplifies the secondoutput signal and outputs a second amplified signal; and a secondcontrol circuit that supplies the second DC control current or DCcontrol voltage to the base of the second transistor thereby controllingsupply of the second output signal to the second amplifier.
 19. A poweramplification circuit comprising: a first transistor having an emitterto which a first radio frequency signal is supplied, a base to which afirst DC control current or DC control voltage is supplied, and acollector from which a first output signal is output, the first outputsignal corresponding to the first radio frequency signal; a firstamplifier that amplifies the first output signal and outputs a firstamplified signal; a first control circuit that supplies the first DCcontrol current or DC control voltage to the base of the firsttransistor thereby controlling supply of the first output signal to thefirst amplifier; a third transistor having an emitter to which a secondradio frequency signal is supplied and that is DC grounded, a base towhich a third DC control current or DC control voltage is supplied andthat is AC grounded, and a collector from which a third output signal isoutput, the third output signal corresponding to the second radiofrequency signal; and a third control circuit that supplies the third DCcontrol current or DC control voltage to the base of the thirdtransistor, thereby controlling supply of the third output signal to thefirst amplifier.